Abstract
Competing interactions in frustrated magnets can give rise to highly degenerate ground states from which correlated liquidlike states of matter often emerge. The scaling of this degeneracy influences the ultimate ground state, with extensive degeneracies potentially yielding quantum spin liquids, while subextensive or smaller degeneracies yield static orders. A long-standing problem is to understand how ordered states precipitate from this degenerate manifold and what echoes of the degeneracy survive ordering. Here, we use neutron scattering to experimentally demonstrate a new "nodal-line"spin liquid, where spins collectively fluctuate within a subextensive manifold spanning one-dimensional lines in reciprocal space. Realized in the spin-orbit-coupled, face-centered-cubic iridate K2IrCl6, we show that the subextensive degeneracy is robust, but remains susceptible to fluctuations or longer-range interactions which cooperate to select a magnetic order at low temperatures. Proximity to the nodal-line spin liquid influences the ordered state, enhancing the effects of quantum fluctuations that in turn act to stabilize the sublattice magnetization through the self-consistent opening of a large spin-wave gap. Our results demonstrate how quantum fluctuations can act counterintuitively in frustrated materials: Even in a case where fluctuations are ineffective at selecting an ordered state from a degenerate manifold, at the brink of the nodal spin liquid, they can act to protect the ordered state and dictate its low-energy physics.
| Original language | English |
|---|---|
| Article number | 021021 |
| Journal | Physical Review X |
| Volume | 15 |
| Issue number | 2 |
| DOIs | |
| State | Published - Apr 2025 |
Funding
Work at Brown University was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Grant No. DE-SC0021223. A portion of this research used resources at the Spallation Neutron Source and High Flux Isotope Reactor, the DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. Access to MACS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. This research used resources of the Advanced Photon Source, a U.S. Department of Energy Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Work at the University of Windsor was funded by the Natural Sciences and Engineering Research Council of Canada (Funding Reference No. RGPIN-2020-04970). We acknowledge the use of computational resources provided by Digital Research Alliance of Canada Work at Brown University was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Grant No. DE-SC0021223. A portion of this research used resources at the Spallation Neutron Source and High Flux Isotope Reactor, the DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. Access to MACS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. This research used resources of the Advanced Photon Source, a U.S. Department of Energy Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Work at the University of Windsor was funded by the Natural Sciences and Engineering Research Council of Canada (Funding Reference No. RGPIN-2020-04970). We acknowledge the use of computational resources provided by Digital Research Alliance of Canada.